Essential hypertension is a major public health problem. Extensive literature has arisen concerning not only its etiology and development, but also its physiologic and behavioral consequences. Several recent investigations demonstrate behavioral correlates of even mild hypertension among young adults. These correlates include subtle disturbances in perceptual, cognitive and psychomotor performance, decreased assertiveness, and heightened cardiovascular responsivity to behavioral stimuli. Recent emphasis on the control of hypertension has also led to widespread (and potentially long term) use of various antihypertensive medications, many of which differ in the mechanisms of their pharmacologic action. However, little is yet known concerning the effects of such agents on behavior: whether they lead to restoration of hypertension-associated deficits and/or generate new areas of behavioral dysfunction. Our purpose is to examine effects of a variety of common-prescribed antihypertensive medications across a broad range of behavioral and social functioning in male, mild essential hypertensive patients. Within each of two treatment conditions, 42 patients will be placed, for consecutive six-week trials, on two medications that differ in the extent of their pharmacologic effects on the central nervous system (lipophilic versus hydrophilic beta-blockers; diuretic versus a centrally-acting sympatholytic (e.g., alpha-agonist)). Comparison conditions will include both placebo-treated hypertensive patients and matched normotensive controls. Behavioral measurements assessing the neurobehavioral, psychophysiologic, and interpersonal functioning of subjects will be obtained at repeated intervals, both before and during treatment. By studying patients prospectively, matching them for a variety of variables that may concomitantly influence behavior (e.g., age), and by using each patient as his own control while on drugs of different pharmacologic types, it will be possible to partition those behavioral consequences attributable to hypertensive disease from those which are due to medications used to treat the disease.